Gonadotropins from the horse and related species are employed as models because of their unique properties (high carbohydrate content; dual biological activities) to obtain information on the chemical, immunological and biological properties of gonadotropins which will relate to their mechanism of action. Techniques of protein chemistry are used to isolate and characterize highly purified equine and related species of luteinizing hormone, follicle stimulating hormone and chorionic gonadotropin. In vitro bioassays, radioreceptor assays and radioimmunoassays are used to obtain structure-function information. The specific aims of the grant proposal are to extensively compare the properties of biosynthetic equine gonadotropins prepared by recombinant DNA technology, to study the role of gonadotropin carbohydrate with intact oligosaccharide units devoid of peptide and by deglycosylation reactions, to isolate and characterize isohormonal forms of equine pituitary gonadotropins and to compare them with secreted forms, to study the gonadotropins in a closely related equid species, the zebra, and to study the activities of equine gonadotropin hybrid molecules prepared from the subunits of molecules with varying activities and potencies. These studies are intended to increase our knowledge of the mechanism of gonadotropin action and reproductive function and should be of future value in devising new approaches to the regulation and maintenance of human reproduction.